Internationalizing Messages in Linux Programs

An introduction to the GNU gettext system for producing multilingual programs.

Linux is becoming increasingly popular
each day. Until now, the typical Linux user has been a system
administrator, student or UNIX hacker. New projects such as GNOME,
KDE and GNUStep are preparing the way for a different, less
technically prepared user.

Running software in English is usually not a problem for
someone with at least moderate computer skills, but end users need
(and want) software that speaks their own
language in order to be productive or feel comfortable with the
system. Moreover, many programs need to know local conventions for
things such as dates or money amounts in order to be useful and
complete.

This article is an introduction to the GNU
gettext system, a set of tools and libraries for both
programmers and translators that enables them to produce
multilingual programs with textual messages in specified languages.
We will deal with languages that use one of the ISO-8859-X
character sets, except for Japanese and Chinese as they require
extra care.

Definitions

Two words appear frequently when talking about support of
different languages in programs:
internationalization and
localization. Since writing these words over
and over (without spelling errors) is annoying and time-consuming,
people abbreviate them as I18N and
L10N. The 18 and 10 indicate the number of
letters between the first and the last letter of each word.

Internationalizing a program means
taking the necessary steps to make it aware of different languages
and national standards.

The process of localization takes place
when an internationalized program is given the information needed
to behave correctly with a certain language and set of cultural
habits.

First Things First

The first thing to do, for both programmers and end users, is
configure the Linux machine to use locales. Most users need only
follow the Locales mini-HOWTO downloadable
from ftp://sunsite.unc.edu/pub/Linux/docs/ and mirrors. Recent
distributions (for example, Red Hat 5.0) include everything to
support locales.

Once the system is enabled to support locales, you must
specify the particular standards and languages you wish to use.
This is done through a set of environment variables. Each one
controls a specific aspect of the locale system:

LANG specifies the global
locale, but can be overridden by the following variables.

LC_COLLATE specifies the
locale used for sorting and comparing.

LC_CTYPE specifies the
character set in use, so that
isupper('<\#192>') returns
true in an Italian locale.

LC_MONETARY provides
information about representing money in a specific locale.

LC_NUMERIC gives information
about numbers: how digits are divided and separated in groups, what
the decimal point is, etc.

LC_TIME specifies which locale
to use to represent time: AM/PM or 24-hour values, for
example.

LC_MESSAGES indicates the
language you prefer for programs' text messages.

LC_ALL overrides any previous
indication and sets a global locale.

Examples of values for global locale are:

en_US indicates English in the
United States.

it_IT is for Italian in
Italy.

fr_CA is for French in
Canada.

Basically, to use the standards of language LL
in country CC, the locale value will be
LL_CC.

The locale used by default, unless overridden by the previous
variables, is called the C (or
POSIX) locale. Thus, it is very easy to
illustrate the behavior of a locale-aware program by using
date, for example (see Listing 1).
First, without setting the LC_ALL variable, the response is in
English. Next, LC_ALL is set to obtain an Italian response, a
French one (French in Canada is specified), then an English one
(English in Canada). The “No such file or directory” for the
Italian locale is not translated, which means the Italian
information is not available; therefore, the default is used
instead.

Geek Guides

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